package cn.dm.example.syncContainer;

import cn.dm.annoations.ThreadSafe;
import com.google.common.collect.Lists;
import lombok.extern.slf4j.Slf4j;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

@Slf4j
@ThreadSafe
public class CollectionsExample1 {

    // 请求总数
    public static int clientTotal = 5000;

    // 同时并发执行的线程数
    public static int threadTotal = 200;

    // 使用 Collections.synchronizedList()
    private static List<Integer> list = Collections.synchronizedList(Lists.newArrayList());
    // 经测试下面直接"new ArrayList"也线程安全,但课程中老师使用的是google中guava包的组件
    // private static List<Integer> list = Collections.synchronizedList(new ArrayList<>());

    public static void main(String[] args) throws Exception {
        ExecutorService executorService = Executors.newCachedThreadPool();
        final Semaphore semaphore = new Semaphore(threadTotal);
        final CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
        for (int i = 0; i < clientTotal; i++) {
            final int count = i;
            executorService.execute(() -> {
                try {
                    semaphore.acquire();
                    update(count);
                    semaphore.release();
                } catch (Exception e) {
                    log.error("exception", e);
                }
                countDownLatch.countDown();
            });
        }
        countDownLatch.await();
        executorService.shutdown();
        log.info("size:{}", list.size());
        /**
         * 结果
         * 11:30:12.538 [main] INFO cn.dm.example.syncContainer.CollectionsExample1 - size:5000
         *
         * 说明使用 Collections.synchronizedList(Lists.newArrayList()) 方法创建的 list 容器是线程安全的
         */
    }

    private static void update(int i) {
        list.add(i);
    }
}
